In general, a backlight unit is comprised of a plurality of cold cathode fluorescent lamps and a light-guiding plate of acrylate. However, the backlight unit may have the following disadvantages such as the loss of light due to the light-guiding plate and the increasing number of cold cathode fluorescent lamps according to the large-sized LCD device.
As disclosed in patent documents 1, 2 and 3, a flat fluorescent lamp is formed of one lamp, which functions as a backlight. The flat fluorescent lamp is very useful for a large-sized backlight unit in that it can be resistant to an external air pressure in a large size, it can obtain a uniform surface luminance, and it can be illuminated brightly even at a low temperature. In this flat fluorescent lamp having a plurality of groups of electrodes, a lighting method is the problem which confronts us.
Patent Document 1: Patent Application No. 2003-436375
Patent Document 2: Patent Application No. 2003-428313
Patent Document 3: Patent Application No. 2003-420114